Muffler



July 26, 1938. L. L. HAAS Er AL 2,124,916

MUFFLER Filed June 14, 1957 INVf/VTOI? 5 (144mm and. g fpa/l vmmPatented July 26, 1938 UNITED STATES PATENT OFFIQE MUFFLER ApplicationJune 14, 1937, Serial No. 148,069

6 Claims.

This invention relates to improvements in mufflers or silencers of thekind which may be used for silencing the exhaust of internal combustionengines.

One of the objects of this invention is to provide a mufiier with anovel arrangement of chambers by means of which sound waves aredestroyed by destructive interference. It is also an object of thisinvention to improve the operation of a mufiier of this type by means ofrestrictions in the inner perforate conduit which serve to increase theeffectiveness of the chambers. Other objects of this invention willappear from the following description and claims.

In the accompanying drawing:

Fig. 1 is a longitudinal central sectional View of the front or inletpart of a mufiler embodying this invention.

Fig. 2 is a similar view of the remainder of the muffler.

Figs. 3 and 4 are transverse sectional elevations respectively on lines33 and L4, Fig. l.

The mufiler disclosed in the accompanying drawing and illustrating oneembodiment of this invention is of the straight through type andincludes an outer housing or casing which may be of any suitable orusual construction, that shown including an outer shell A having at oneend thereof an inlet head B which may be provided with an integrallyformed duct b to which an exhaust pipe from an engine may be connected.At the other end of the outer shell, the muffler is provided with anoutlet or discharge head C which may also have an integrally formed ductthrough which gases are discharged from the mufller and to which theusual tail pipe may be connected, if desired.

The inlet duct b and discharge duct 0 in the muiiler shown are connectedby means of a conduit or inner shell I which is provided with aplurality of perforations 8 which may be of any suitable form. Forexample, as clearly shown in Fig. 4, the perforations may be formed bymaking longitudinal slits in the conduit and forcing the metal at oneside of each slit outwardly to form louvers 9 which cause the gasesdischarged through the perforations 8 to take a more or less tangentialdirection with reference to the conduit i. The perforations 3 arepreferably arranged in groups spaced at intervals lengthwise of theconduit. A perforate conduit of any other construction may, of course,be provided, if desired.

An intermediate shell of any suitable or desired form may be employed inthe space between the outer shel1-A and the conduit 1 of the muffler.

The intermediate shell may comprise two or more parts and preferably theintermediate shell forms near the discharge end of the muffler one ormore high frequency resonator chambers. This part of the intermediateshell, in the particular construction shown, is in the form of two halfshells H] and I5, which may be suitably connected at theirlongitudinally extending edge portions in any suitable manner to formjoints at l2. These half shells may be provided with inwardly extendingshoulders i l, I and I6, thus forming two high frequency resonatorchambers H and i8 about two groups of perforations 8. It will, ofcourse, be understood that this part of the intermediate shell may be ofany other suitable or usual construction.

The other intermediate shell part may be in the form of a cylinder ortube 26 which may be secured in place in any suitable or desired manner.In the construction shown, a transverse wall or bafile 2| is providedintermediate of the ends of this shell part 29 and connects the partwith the conduit 7, and an end of this shell part may be provided withinwardly pressed parts 22 which extend into contact with the conduit 1and which are arranged between longitudinally extending parts 2 whichare spaced from the conduit and form therewith openings in the form ofchannels or passages 25. In the muiller shown, the opposite end of theintermediate shell part 29 is supported from the outer shell A by meansof a transverse partition or bafile 2?, which also serves the purpose ofdividing the space between the outer shell A and the intermediate shellparts into two outer chambers 28 and 29. In the construction shown inFig. 2, the baffle 27 is arranged adjacent to an end of the intermediateshell part 2i! and the open end of this shell part, consequently, formsan opening communicating with the front end of the chamber 23. Thechannels or openings establish communication between the chamber 29 andanother chamber or space 39 formed between the conduit and theintermediate shell part 2! and form with his chamber a bottle neck typeof resonator chamber.

The silencing action of the muflier is further enhanced by providing inthe conduit 7 one or more restrictions or diffusers, such as describedin the Starkweather and Haas Patents Nos. 2,047,442 and 2,047,443. Theserestrictions, of course, may be of any suitable or desired form, and inthe mufiler illustrated, there are provided sleeves 33 and 3 havingportions secured to the inner wall of the conduit 1 and annular portionsof reduced diameter. One of these restrictions is located in the portionof the conduit in advance of the intermediate baflle 2| and the otherrestriction is placed in rear of the baffle, so that the restriction 33will tend to increase the quantity of gas and sound waves which passthrough the perforations 8 located in advance of the restriction. Inthis manner, an increased flow of gas and sound waves into the chambers30 and 3! results, which in turn results in a corresponding increase inthe flow of gas or sound waves into the outer low frequency chambers 29and 28, so that the silencing action of the muflier is materiallyimproved with a relatively small increase in the back pressure.

As a result of the construction described, gas impulses and sound wavesentering into the muffler through the inlet 1) thereof will pass intothe conduit 1 and upon reaching the perforations thereof, portions ofthe sound waves and the peaks of the pressure pulses will pass throughthose perforations 8 leading into the chamber 39 and parts of thesepressure impulses and some of the sound waves will also pass through thechannels or bottle necks into the outer or low frequency resonatorchamber 29. The restriction 33 tends to hold back slightly the rush ofpressure impulses through the conduit and consequently, increases theextent to which parts of pressure impulses enter into the chambers 36and 29. The portions of the gas pressure impulses entering the chambersand 29 are returned to the conduit 7 through apertures 3 and enter intothe troughs or low pressure portions between gas pulsations, and soundwaves entering the low frequency chamber 29 will be returned through thechannels or bottle necks 25, chamber 38, and apertures 8 into theconduit and will be out of phase with sound waves passing directlythrough the conduit, so that such sound waves will in general besilenced by destructive interference. The gas impulses and sound waveswhich continue through the inner conduit past the partition 2! may thenpass in part through the perforations in the inner conduit into achamber 3! between the conduit and intermediate shell from which theymay pass through the opening or open end of the intermediate shell part26 into the outer or low frequency resonator chamber 28 arranged aboutthe intermediate shell parts it? and N. This chamber 28 acts in asimilar manner upon the gas pulsations and low frequency sound waves, asthe chamber 29, but may be of different dimensions than the chamber 29and may consequently, act upon a group or band of low frequency soundwaves of different wave lengths than those silenced by the action of thechamber 29. The restriction 34 also acts in the same manner as therestriction 33 and forces a larger portion of gas to pass throughopenings or perforations in the conduit and also materially increasesthe effectiveness of the chamber 28. The chambers 28 and 29, in additionto their action on sound waves also act to equalize the flow of gasthrough the conduits by taking in the crests or peaks of pressurepulsations and returning them into the conduit between pulsations.Consequently, by the time the gases pass through the portionof the innerconduit about which the high frequency chambers l1 and i8 are formed,these high frequency chambers will be particularly effective in actingon high fre quency sound waves and upon gas pressure pulsations ofgreatly reduced intensity, so that an exceptionally effective silencingresults.

The muflier described has the advantages of being of relatively simpleand inexpensive construction and of being very effective in silencingthe exhaust. The provision of an intermediate shell part about theconduit eliminates shell noises and the openings in the intermediateshell are located at one end of each outer chamber, thus causing theseouter chambers to act very effectively as low frequency resonatorchambers.

We claim as our invention:

1. A mufier including a single housing having an inlet and an outlet, aconduit having perforations arranged in groups spaced at intervalslengthwise of said conduit and connecting said inlet and outlet, anintermediate shell part arranged in said housing about said conduit nearsaid outlet which encloses a perforate portion of said conduit to formtherewith a high frequency resonator chamber, and a second intermediateshell part located in said housing forwardly of said first part alsoenclosing a perforate portion of said conduit and having an openingleading to a space between the first intermediate shell part and saidhousing, and a transverse loaflie connecting said second part and saidhousing and located forwardly of said opening to form a low frequencyresonator chamber about said first part and into which sound waves andgases may enter through said opening.

2. A muilier including a single housing having an inlet and an outlet, aconduit having perforations arranged in groups spaced at intervalslengthwise of said conduit and connecting said inlet and outlet, anintermediate shell part arranged in said housing about said conduit nearsaid outlet which encloses a perforate portion of said conduit to formtherewith a high frequency resonator chamber, and a second intermediateshell part located in said housing forwardly of said first part alsoenclosing a perforate portion of said conduit and having an openingleading to a space between the first intermediate shell part and saidhousing, a transverse baffie connecting said second part and saidhousing and located forwardly of said opening to form a low frequencyresonator chamber about said first part and into which sound waves andgases may enter through said opening, and a restriction in the portionof said conduit about which said second intermediate shell part extends,and located rearwardly of perforations enclosed by said second part toproduce an increased passage of gases and sound waves throughperforations ahead of said restriction into the space within said secondpart and through the opening in said second part.

3. A muflier including a single housing having an inlet and an outlet, aperforate conduit in said housing connecting said inlet and said outlet,an intermediate shell part arranged in said housing about said conduitnear said outlet which encloses a perforate portion of said conduit toform therewith a high frequency resonator chamber, a second intermediateshell part located in said housing forwardly of said first part andarranged about a perforate portion of said conduit, and a baffleconnecting said second part and said housing and dividing the spacebetween said second shell part and said housing into a plurality ofouter chambers, one of said chambers including the space arrangedbetween said first mentioned intermediate shell part and said housing,said second shell part having openings near opposite ends thereof andeach communicating with one of said outer chambers.

4. A muflier including a single housing having an inlet and an outlet, aperforate conduit in said housing connecting said inlet and said outlet,an intermediate shell part arranged in said housing about said conduitnear said outlet which encloses a perforate portion of said conduit toform therewith a high frequency resonator chamber, a second intermediateshell part located in said housing forwardly of said first part andarranged about a perforate portion of said conduit, a baffle connectingsaid second part and said housing and dividing the space between saidsecond shell part and said housing into a plurality of outer chambers,one of said chambers including the space arranged between said firstmentioned intermediate shell part and said housing, said second shellpart having openings near opposite ends thereof and each communicatingwith one of said outer chambers, and transversely extending meansforming a dividing wall between said second intermediate shell part andsaid conduit and arranged with perforations forwardly and rearwardlythereof.

5. A muffler including a single housing having an inlet and an outlet, aperforate conduit in said housing connecting said inlet and said outlet,an intermediate shell part arranged in said housing about said conduitnear said outlet and enclosing a perforate portion of said conduit toform therewith a high frequency resonator chamber, a second intermediateshell part located in said housing forwardly of said first part andarranged about a perforate portion of said conduit, a bafile connectingsaid second part and said housing and dividing the space between saidsecond shell part and said housing into a plurality of outer chambers,one of said chambers including the space arranged between said firstmentioned intermediate shell part and said housing, said second shellpart having openings near opposite ends thereof and each communicatingwith one of said outer chambers, and a restriction in said conduit inthe portion thereof about which said second shell part extends forinducing an increased flow of gases and sound waves through perforationsin advance of said restriction for passage to said outer chambers.

6. A mufiler including a single housing having an inlet and an outlet, aperforate conduit in said housing connecting said inlet and said outlet,an intermediate shell part arranged in said housing about said conduitnear said outlet and enclosing a perforate portion of said conduit toform therewith a high frequency resonator chamber, a second intermediateshell part located in said housing forwardly of said first part andarranged about a perforate portion of said conduit, a baflle connectingsaid second part and said housing and dividing the space between saidsecond shell part and said housing into a plurality of outer chambers,one of said chambers including the space arranged between said firstmentioned intermediate shell part and said housing, said second shellpart having openings near opposite ends thereof and each communicatingwith one of said outer chambers, transversely extending means forming adividing wall between said second intermediate shell and said conduitand arranged with perforations forwardly and rearwardly thereof, andrestrictions in said conduit, one arranged in advance of saidtransversely extending means, and the other in rear thereof to increasethe flow of gases and sound waves into the spaces within said secondintermediate shell part in front of and in rear of said transverselyextending means to increase the effectiveness of said outer chambers insilencing sound waves.

LUCIEN L. HAAS. GAIL C. STARKWEATHER.

